Another hi-tech hybrid feast from Lexus? What's on the menu then?

Well, if the gadget-laden LS460 isn't quite gadgety enough for you, this green LS hybrid might satisfy your appetite for technology. For a start, it has four-wheel drive, a petrol V8 paired with an electric motor, and an eight-speed continuously variable transmission. It's the full king's banquet. And it's not just the drivetrain that's stuffed with everything from Toyota's extensive gadget collection. The LS600h also gets smarter-than-you LED headlamps, active steering, air suspension and a camera that can tell if you're looking away and about to hit an obstacle. They really have thought of everything.

Wow. What next? Will it drive itself?

Not quite, but it'll keep you awake during those long motorway cruises after a plate full of cucumber sandwiches at the afternoon board meeting. A facial recognition camera detects how close you are to the land of nod and warns you accordingly. Snoozing in the rear is encouraged with massaging pews to pummel away all that executive stress. That said, if the peaceful tranquility inside the cabin becomes a little too mellowing, you can always peruse the dashboard display that shows you the energy flow from the brakes to the battery via a digital graph. If that doesn't stimulate you, what will?

Ok, so the LS600h is full of tricks, but how does it drive?

Quite well, actually, although like any hybrid it's hampered by weight, tipping the scales at over two tonnes. The green giant will hit 62mph in 6.3 seconds, so it's no slouch, but you get the feeling that if it wasn't so bloated it would be noticeably swifter. To put that into perspective, a Mercedes S600 will get to 62mph in 4.6 seconds. How much that figure matters will depend on how much you crave the environmental kudos hybrids bring these days. Unlike the LS460, the 600h has four-wheel drive and has peerless traction as a result. The ride lacks the composure of a Merc S-class, because it's a tad compromised; the air suspension is too taut in Sport mode and too wallowy in Comfort, but it's hardly unrefined.

So it's a bit slower and less composed than the competition, but it's economical, right?

Yep. Well, for a huge luxury barge anyway. Lexus claims 30.3mpg on the combined cycle, which is disappointingly less than a decent diesel luxury car. Ok, so the LS600h can waft around on electric power alone at low speeds, but why pay £81k for a more complicated environmental solution when it doesn't really work? It's the biggest chink in the Lexus's armour. Potter through town very gently in the LS600h and it'll run solely on battery power, in an eerily silent, very comfortable executive crawl. Put your foot down on the autobahn, however, and you're off to Hybrid Hades as the 5.0-litre V8 catapults you into single-figure consumption territory. Makes you wonder about all those big names queuing up to drive hybrids to bolster their eco-credentials...

Ah, the electric motor. Tell me about that then.

At the heart of the Lexus hybrid is a power split device which directs torque in two directions; mechanically to the wheels, and electrically to a generator. All that matters is that you enjoy instant pull from the torquey electric motor from low down, and there's strong shove from 50-70mph, which passes in a scant 4.3 seconds.

So why shouldn't I just buy a Merc S320 CDI?

In a word, green. There's an environment to be saved, and if you buy this you'll feel slightly smug about that. On the downside, the green in your pocket will deteriorate significantly. At £81,400, the Lexus will cost over £26k more than an S320 CDI, which is easily enough to buy a Toyota Prius as well to pootle around town, if you're so inclined. In practical terms, you'll sacrifice space for a cleaner conscience too: the LS600h has less boot capacity than a Golf as the hybrid gubbins gobbles up room, so the Merc's the one to take to the golf course.

Verdict

The LS could quite possibly convert gas-guzzlers to battery power, so impressive and addictive is the power pack's extra boost. On paper the performance and economy stats aren't too far away from a current top European diesel limo like the Audi A8 4.2 TDI, although no diesel rival can boast the techno kit or power delivery that the Lexus serves up. In terms of refinement, street cred and engaging handling, however, the Japanese pretender is still edged out by its European peers, but only just. In the post-Live Earth world, it's worth considering for the greener businessman, but there's no getting away from the fact that £81k is frankly eye-watering.